Semiconductor device and method of manufacturing the same

ABSTRACT

In a semiconductor device in which a plurality of semiconductor chips are stacked, performance is enhanced without deteriorating productivity. The semiconductor device has a plurality of elements, an interlayer insulating film, a pad, and a bump electrode electrically connected with the pad sequentially formed on a main surface of a silicon substrate and has a back-surface electrode formed on a back surface of the silicon substrate and electrically connected with the bump electrode. The bump electrode has a protruding portion penetrating through the pad and protruding toward the silicon substrate side. The back-surface electrode is formed so as to reach the protruding portion of the bump electrode from the back surface side of the silicon substrate toward the main surface side and to cover the inside of a back-surface electrode hole portion which does not reach the pad, so that the back-surface electrode is electrically connected with the bump electrode.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2008-323581 filed on Dec. 19, 2008, and is a continuationapplication of U.S. application Ser. No. 12/640,766, filed Dec. 17,2009, now U.S. Pat. No. 8,106,518 the contents of which are herebyincorporated by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a semiconductor device and techniquesof manufacturing the same and, particularly, relates to techniqueseffectively applied to a semiconductor device having a structure inwhich a plurality of semiconductor chips are stacked.

BACKGROUND OF THE INVENTION

In mobile devices such as mobile phones and digital cameras, SiP (Systemin Package) in which a plurality of chips are stacked and mounted in asemiconductor package is widely used. When the chips are disposed in themanner that they are stacked, the mounting area can be reduced comparedwith the case in which they are horizontally disposed. Moreover, a largenumber of chips can be mounted in the same mounting area. However, whenthe chips are mutually connected by bonding wires, the wiring space foronce suspending the bonding wires is needed in a chip peripheral region,and thus the mounting area becomes larger than the chip size. Moreover,there are problems that resistance and inductance are increased as thebonding wires are long and that this is not suitable for high-speedoperations.

In order to solve these problems, development of siliconthrough-electrode techniques for directly connecting chips by formingelectrodes which penetrate through the inside of the chips is underway.In this structure in which the chips are mutually and directlyconnected, the wiring space is not needed in the chip peripheral part,and the space of the mounting area thereof can be reduced. Furthermore,since the inter-chip wiring is the shortest, the wiring resistance andinductance can be suppressed low, and high-speed operations can becarried out.

For example, Japanese Patent Application Laid-Open Publication No.2000-260934 reports the technique in which, after forming through-holesin chips, through-electrodes are formed by embedding solder or alow-melting-point metal by electrolytic or electroless plating method,and the chips are mutually connected by melting the embedded metal byheating.

Moreover, for example, Japanese Patent Application Laid-Open PublicationNo. 2007-53149 reports the technique in which a bump formed on an upperchip is pressed against a hollow through-electrode formed in a lowerchip to cause the bump and the through-electrode to undergo plasticdeformation, so that the bump and the through-electrode are physicallycaulked so as to mutually connect the chips.

Conceivable methods of forming the above-described bump include a studbump method and a plating bump method. For example, Japanese PatentApplication Laid-Open Publication No. 2007-73919 discloses a method offorming a bump having a sharp end by the plating bump method. Such bumphas a high deformability and is suitable for the inter-chip connectiontechnique described in the above-mentioned Patent Document 2.

In the technique of the above-mentioned Patent Document 2 studied by theinventors of the present invention, the through-electrode is formed froma back surface of a semiconductor wafer after semiconductor elements,multi-layer wirings, and bonding pads are formed on a main surface ofthe semiconductor wafer. When the through-electrode is formed at the endin this manner, the influence on the device caused by particles andcontamination generated upon formation of the through-electrode can bereduced, and the designing and manufacturing processes of the device andmulti-layer wiring are not required to be changed. Moreover, there isalso a big advantage that the through-electrode can be treated as a partof the packaging technique, for example, the through-electrode can bemanufactured even in an existing product chip for which inter-chipwiring by wire bonding is expected.

On the other hand, in order to electrically connect the device, which isformed on the semiconductor wafer main surface, and thethrough-electrode to each other, the through-electrode and a bonding padhave to be electrically connected to each other. The bonding pad isdisposed on the surface of an interlayer insulating film. In order toform the through-electrode from the back surface, a hole whichpenetrates through the silicon substrate part and the interlayerinsulating film and stops at the bonding pad surface is formed. Thethrough-electrode can be formed in this manner.

However, according to further studies carried out by the presentinventors about the method of forming the through-electrode describedabove, it has been found out that the method has below problems. When ahole is to be formed from the back surface of the silicon substrate inorder to form the through-electrode, as the processability of theinterlayer insulating film per se, which is positioned in a lower layer,is low and the part disposed on the bottom surface of a deep hole formedin the silicon substrate is to be processed, etching species does notreadily enter. Furthermore, the etching has to be stopped at the pointit reaches the thin bonding pad.

As a technical trend of the future, it is conceivable that the degree ofintegration of the devices mounted on semiconductor devices will beincreased and that the number of the through-electrodes formed per onechip will be increased. As a result, the through-electrode will have asmall diameter and a high aspect ratio. Given such background, it hasbeen found out that it would be difficult to form the hole portion forthe through-electrode only by the back-surface processing. Thedifficulty of processing the through-electrode and the need for higherprocessing techniques are the cause that lowers the productivity ofabove-mentioned high-performance semiconductor devices.

SUMMARY OF THE INVENTION

Accordingly, a preferred aim of the present invention is to provide atechnique that enhances performance of a semiconductor device, in whicha plurality of semiconductor chips are stacked, without deterioratingthe productivity.

The above and other preferred aims and novel characteristics of thepresent invention will be apparent from the description of the presentspecification and the accompanying drawings.

The present application discloses a plurality of inventions, and asummary of an embodiment among them will be simply described below.

A semiconductor device has a plurality of elements formed on a firstmain surface of a semiconductor substrate, an interlayer insulating filmformed so as to cover the elements, a pad formed on a surface of theinterlayer insulating film and electrically connected with the pluralityof elements, a first electrode having a bump shape formed so as to beelectrically connected with the pad, and a second electrode formed on asecond main surface-side of the semiconductor substrate and formed so asto be electrically connected with the first electrode. Specifically, thefirst electrode has a protruding portion penetrating through the pad andprotruding toward the semiconductor substrate-side, and the secondelectrode is formed so as to reach the protruding portion of the firstelectrode part from the second main surface-side of the semiconductorsubstrate toward the first main surface-side and cover the inside of thesecond-electrode hole portion which does not reach the pad; thus, thesecond electrode is electrically connected with the first electrode.

The effects obtained by typical aspects of the present invention will bebriefly described below.

More specifically, in a semiconductor device in which a plurality ofsemiconductor chips are stacked, performance can be enhanced withoutdeteriorating the productivity.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a main part of a semiconductordevice which is a first embodiment of the present invention;

FIG. 2 is a plan view of a main part of the semiconductor device whichis the first embodiment of the present invention;

FIG. 3 is a plan view of another main part of the semiconductor devicewhich is the first embodiment of the present invention;

FIG. 4 is a cross-sectional view of a main part of the semiconductordevice which is the first embodiment of the present invention in amanufacturing step;

FIG. 5 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 4;

FIG. 6 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 5;

FIG. 7 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 6;

FIG. 8 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 7;

FIG. 9 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 8;

FIG. 10 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 9;

FIG. 11 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 10;

FIG. 12 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 11;

FIG. 13 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 12;

FIG. 14 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 13;

FIG. 15 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 14;

FIG. 16 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 15;

FIG. 17 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 16;

FIG. 18 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 17;

FIG. 19 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 18;

FIG. 20 is a cross-sectional view of a main part of a semiconductordevice of a first structure according to a second embodiment of thepresent invention;

FIG. 21 is a cross-sectional view of a main part of a semiconductordevice of a second structure according to the second embodiment of thepresent invention;

FIG. 22 is a cross-sectional view of a main part of the semiconductordevice of the second structure according to the second embodiment of thepresent invention in a manufacturing step and is a cross-sectional viewof the main part in a step subsequent to that of FIG. 4;

FIG. 23 is a cross-sectional view of the main part of the semiconductordevice of the second structure according to the second embodiment of thepresent invention in a manufacturing step and is a cross-sectional viewof the main part in a step subsequent to that of FIG. 12;

FIG. 24 is a cross-sectional view of a main part of a semiconductordevice of a third structure according to the second embodiment of thepresent invention;

FIG. 25 is a cross-sectional view of a main part of a semiconductordevice of a fourth structure according to the second embodiment of thepresent invention;

FIG. 26 is a cross-sectional view of a main part of the semiconductordevice of the fourth structure according to the second embodiment of thepresent invention in a manufacturing step and is a cross-sectional viewof the main part in a step subsequent to that of FIG. 4;

FIG. 27 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 26;

FIG. 28 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 27;

FIG. 29 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 28;

FIG. 30 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 29;

FIG. 31 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 30;

FIG. 32 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 31;

FIG. 33 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 32;

FIG. 34 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 33;

FIG. 35 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 34;

FIG. 36 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 35;

FIG. 37 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 36;

FIG. 38 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 37;

FIG. 39 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 38;

FIG. 40 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 39;

FIG. 41 is a cross-sectional view of a main part of the semiconductordevice in a manufacturing step continued from FIG. 40;

FIG. 42 is a cross-sectional view of a main part of anothersemiconductor device according to the second embodiment of the presentinvention;

FIG. 43 is a cross-sectional view of a main part of still anothersemiconductor device according to the second embodiment of the presentinvention;

FIG. 44 is a cross-sectional view of a main part of still anothersemiconductor device according to the second embodiment of the presentinvention;

FIG. 45 is a cross-sectional view of a main part of a semiconductordevice according to a third embodiment of the present invention;

FIG. 46A illustrates the semiconductor device according to the thirdembodiment of the present invention and is an explanatory diagramillustrating a structure of a bump electrode;

FIG. 46B illustrates the semiconductor device according to the thirdembodiment of the present invention and is an explanatory diagramillustrating a structure of a back-surface electrode;

FIG. 47 illustrates the semiconductor device according to the thirdembodiment of the present invention, wherein an explanatory diagramillustrating a connection state is illustrated on the left side, and anexplanatory diagram illustrating a joint between the back-surfaceelectrode and the bump electrode is illustrated on the right side;

FIG. 48A is an explanatory diagram illustrating the semiconductor deviceaccording to the third embodiment of the present invention illustratinga structure of the bump electrode having a triangular shape in a planeand a joint between the structure and the back-surface electrode;

FIG. 48B is an explanatory diagram illustrating the semiconductor deviceaccording to the third embodiment of the present invention illustratinga structure of the bump electrode having a rectangular shape in a planeand a joint between the structure and the back-surface electrode;

FIG. 48C is an explanatory diagram illustrating the semiconductor deviceaccording to the third embodiment of the present invention illustratinga structure of the bump electrode having an oval shape in a plane and ajoint between the structure and the back-surface electrode;

FIG. 49A is an explanatory diagram illustrating another semiconductordevice according to the third embodiment of the present embodimentillustrating a structure of a back-surface-electrode hole portion havinga rectangular shape in a plane and a joint between the structure and thebump electrode;

FIG. 49B is an explanatory diagram illustrating the anothersemiconductor device same with FIG. 49A according to the thirdembodiment of the present embodiment illustrating a structure of theback-surface-electrode hole portion having an oval shape in a plane anda joint between the structure and the bump electrode;

FIG. 50A is an explanatory diagram illustrating the anothersemiconductor device same with FIGS. 49A and 49B according to the thirdembodiment of the present invention illustrating a structure of a bumpelectrode having a sidewall having a low-inclination taper angle and ajoint between the structure and a back-surface electrode; and

FIG. 50B is an explanatory diagram illustrating the anothersemiconductor device same with FIG. 50C illustrating a structure of thebump electrode having a sidewall having a steep-inclination taper angleand a joint between the structure and the back-surface electrode.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Note that components having the same function are denoted by the samereference symbols throughout the drawings for describing the embodiment,and the repetitive description thereof will be omitted as much aspossible. Hereinafter, embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First Embodiment

A configuration of a semiconductor device of a first embodiment will bedescribed with reference to FIGS. 1 to 3. FIG. 1 illustrates across-sectional view of a main part of a silicon substrate(semiconductor substrate) 1 which the semiconductor device of the firstembodiment has. FIG. 2 illustrates a plan view of a main part of a mainsurface (first main surface) s1-side of the silicon substrate 1. FIG. 3illustrates a plan view of a main part of a back surface (second mainsurface) s2-side of the silicon substrate 1. The main surface s1 and theback surface s2 of the silicon substrate 1 are positioned on the sidesopposite to each other in a thickness direction of the silicon substrate1.

A plurality of semiconductor elements (elements) such as field effecttransistors (FETs), capacitors, and non-volatile memory cells are formed(not illustrated) on the main surface s1 of the silicon substrate 1.Further, an interlayer insulating film 2 is formed on the main surfaces1 of the silicon substrate 1 so as to cover the above-describedplurality of elements. The interlayer insulating film is an insulatingfilm mainly formed of silicon oxide. Pads 3 (bonding pads) are formed onthe surface of the interlayer insulating film 2. The pads 3 areelectrically connected with the plurality of elements on the mainsurface s1 of the silicon substrate 1 via multilayer wiring and plugs(not illustrated) in the interlayer insulating film 2.

A bump electrode (first electrode) 4 is formed on the pad 3 so as to beelectrically connected with the pad. The bump electrode 4 has aso-called bump shape that protrudes to have a predeterminedthree-dimensional shape in the main surface s1-side of the siliconsubstrate 1. The bump electrode 4 is a conductor formed of, for example,a single-layer structure of gold (Au), copper (Cu), aluminum (Al),nickel (Ni), or the like or a multi-layer structure of any of thesematerials.

In the semiconductor device of the first embodiment, the bump electrode4 has a configuration as described below. That is, the bump electrode 4of the first embodiment has a protruding portion d1 which penetratesthrough the pad 3 and protrudes toward the silicon substrate 1-side. Asan example, FIG. 1 illustrates the structure in which the protrudingportion d1 of the bump electrode 4 is formed so as to also penetratethrough the interlayer insulating film 2 and, when viewed incross-section, reaches the inside of the silicon substrate 1. Moreover,a bump-electrode seed layer (first-electrode seed layer) 5 is formed ona bottom portion of the bump electrode 4 and the protruding portion d1thereof. The bump-electrode seed layer 5 is a component that isnecessary in terms of manufacturing process, and this will be explainedin detail when a manufacturing method of the first embodiment isdescribed later.

A back-surface electrode (second electrode) 6 is formed on the backsurface s2 of the silicon substrate 1. The back-surface electrode 6 isformed so as to be electrically connected with the bump electrode 4 in aconfiguration below. A back-surface-electrode hole portion(second-electrode hole portion) 7 is formed so as to reach at least thedepth of the protruding portion d1 of the bump electrode 4 from theback-surface s2-side of the silicon substrate 1 toward the main surfaces1-side and not to reach the pad 3. The back-surface electrode 6 isformed so as to cover the inside of the back-surface-electrode holeportion 7. Thus, the back-surface electrode 6 and the protruding portiond1 of the bump electrode 4 contact with each other in theback-surface-electrode hole portion 7, and the state in which both ofthem are electrically connected with each other is achieved. As anexample, FIG. 1 illustrates the structure in which theback-surface-electrode hole portion 7 penetrates through the siliconsubstrate 1 from the second main surface s2 to the first main surface s1and reaches the interlayer insulating film 2. Also, as an example, thestructure in which, when viewed in a plan view, a diameter of theback-surface-electrode hole portion 7 is larger than a diameter of theprotruding portion d1 of the bump electrode 4 is illustrated. Therefore,components are disposed so that the protruding portion d1 of the bumpelectrode 4 is contained inside the back-surface-electrode hole portion7 when viewed in a plan view.

Moreover, an insulating film 8 is formed at a boundary portion betweenthe back-surface electrode 6 and the silicon substrate 1, so that theback-surface electrode 6 and the silicon substrate 1 are electricallyinsulated from each other. Moreover, a back-surface-electrode seed layer9 is formed in a layer below the back-surface electrode 6. Theback-surface-electrode seed layer 9 is a component necessary in terms ofmanufacturing process, and this will be explained in detail when themanufacturing method of the first embodiment is described later.

Note that the back-surface electrode 6 is formed not only the inside ofthe back-surface-electrode hole portion 7, but also on the second mainsurface s2 of the silicon substrate 1, which is outside of the holeportion. A metal wire can be connected to this part by wire bonding. Asillustrated in FIG. 3, the back-surface electrodes 6 disposed atdifferent locations may be mutually connected on the second main surfaces2 of the silicon substrate 1 so as to form wiring.

The structure of the through-electrode which the semiconductor device ofthe first embodiment has been described above. The effects of theconfigurations will be described in detail in the following descriptionof a manufacturing process or later in the description of a method ofconnection with another substrate.

Next, the method of manufacturing the semiconductor device of the firstembodiment having the above-described configuration will be describedwith reference to FIG. 4 to FIG. 19. The drawings are cross-sectionalviews of a main part of the silicon substrate 1 of the partcorresponding to above-described FIG. 1 in the manufacturing process.

In the process, first, the plurality of semiconductor elements such asfield effect transistors, capacitors, and non-volatile memory cells areformed (not illustrated) on the main surface s1 of the silicon substrate1.

Then, as illustrated in FIG. 4, the interlayer insulating film 2 isformed on the main surface s1 of the silicon substrate 1 so as to coverthe plurality of semiconductor elements. The multilayer wiring is formed(not illustrated) in the interlayer insulating film 2 so as to beelectrically connected with the semiconductor elements. Subsequently,the pads 3 are formed on the surface of the interlayer insulating film2. The pads 3 are electrically connected with the multilayer wiring,which is in the interlayer insulating film 2, and are electricallyconnected with the plurality of semiconductor elements via themultilayer wiring.

Next, as illustrated in FIG. 5, a bump-electrode hole portion(first-electrode hole portion) 10 which penetrates through the pad 3from the surface-side of the interlayer insulating film 2 and has adepth toward the silicon substrate 1 is formed. To form thebump-electrode hole portion 10, first, a photoresist film (notillustrated) which is patterned by a photolithography method is formedso as to expose part of the pad 3 on the surface of the interlayerinsulating film 2. Then, the bump-electrode hole portion 10 is formed bycarrying out anisotropic etching by an ICP-RIE (inductively coupledplasma-reactive ion etching) method by using the photoresist film as anetching barrier. Then, the remaining resist mask is removed by, forexample, an organic solvent or oxygen ashing. Herein, particularly, thebump-electrode hole portion 10 which penetrates through the pad 3 andthe interlayer insulating film 2 from the surface of the interlayerinsulating film 2 and has a depth that reaches the silicon substrate 1is formed.

Next, as illustrated in FIG. 6, the bump-electrode seed layer 5 isformed on the entire surface of the interlayer insulating film 2including the inner surface of the bump-electrode hole portion 10. Asthe seed layer to be formed, for example, a titanium (Ti) film or atitanium tungsten (TiW) film is used. Such bump-electrode seed layer 5is formed, for example, by a sputtering method, a CVD (chemical vapordeposition) method, or a vapor deposition method.

Next, as illustrated in FIG. 7, a photoresist film 11 is formed on theentire surface of the main surface s1-side of the silicon substrate 1.The photoresist film 11 is formed by application using a spinner orspray. The formed photoresist film 11 is applied so as to have a filmthickness of about 10 to 30 μm. This thickness corresponds to the heightof the bump electrode 4 (see above-described FIG. 1), which will beformed later.

Then, the photoresist film 11 is patterned to have a desired shape by aseries of photolithography steps, i.e., exposure and development.Particularly, as is described later in detail, the shape of the holepatterned on the photoresist film 11 serves as the outer shape of thebump electrode 4, which will be formed later. In FIG. 7, the hole of thephotoresist film 11 having such outer shape is illustrated as anexample.

Here, a method of forming the bump electrode 4 will be illustrated as anexample so that the bump electrode has the tapered shape as illustratedin above-described FIG. 1 in which the closer the interval between themutually facing sidewalls to the silicon substrate 1, the wider theinterval. Details of this method are described in above-described PatentDocument 3. Usually, after the photoresist film 11 or the like isapplied, the film is subjected to a heating treatment called pre-baking(or soft baking) before subjected to the exposure step, therebysolidifying the photoresist film. In this process, a temperatureinclination is imparted to the silicon substrate 1-side (the backsurface-side of the photoresist film 11) and the surface side of thephotoresist film 11. As a result, an inclination is generated inaccordance with the developing-solution resistance of the photoresistfilm 11 when viewed in the film-thickness direction. Thus, the holehaving the above-described tapered shape can be formed in thephotoresist film 11. Note that examples of shapes in a plan view of theformed hole include a circular shape and a polygonal shape. Differencesin effects caused by the shapes will be explained in detail in afollowing third embodiment.

Next, as illustrated in FIG. 8, a metal is embedded in the hole of thephotoresist film 11 by the electrolytic plating method (also referred toas electroplating) so as to form the bump electrode 4. The embeddedmetal is, for example, a single-layer structure of Au, Cu, Al, Ni, orthe like or a multi-layer structure of any of these metals. However, asis described in detail later, since the bump electrode 4 connects chipsby utilizing its plastic deformation, the uppermost surface of the bumpelectrode 4 is desirably Au which readily undergoes plastic deformation.Then, the photoresist film 11 is removed, for example, by an organicsolvent or oxygen ashing.

The bump electrode 4 having the protruding portion d1 as described withreference to above-described FIG. 1 which the semiconductor device ofthe first embodiment has can be formed in the above-described manner.

Next, as illustrated in FIG. 9, part of the bump-electrode seed layer 5that is not covered with the bump electrode 4 is removed by etching.Herein, the etching is more preferably carried out with using the bumpelectrode 4 as an etching mask, without forming another etching mask.Thus, the number of steps can be reduced. A conceivable etching methodin this process is, for example, dry etching using ICP-RIE or wetetching using an etching solution.

Next, as illustrated in FIG. 10, an adhesion layer 12 is applied ontothe surface of the interlayer insulating film 2, and a support wafer 13such as quartz glass or a silicon wafer is pasted on the adhesion layer12. When the support wafer 13 is pasted on the adhesion layer 12,strength deterioration, warpage, etc. which may be generated when thethickness of the silicon substrate 1 is reduced in a later step can besuppressed. Further, the adhesion layer 12 plays a role of protectingthe plurality of elements, the multi-layer wiring, the bonding pads 3,the bump electrodes 4, etc. formed on the main surface s1 of the siliconsubstrate 1. For example, an epoxy-based adhesive agent or a photoresistfilm is conceivable as such an adhesion layer 12, and the material ofthe adhesion layer 12 has to enable peel-off of the support wafer 13after formation of the through-electrode.

Next, as illustrated in FIG. 11, the silicon substrate 1 is subjected toa back grind treatment from the back surface s2-side, thereby reducingthe thickness of the silicon substrate 1. Examples of the method of theback grind treatment include grinding, polishing, etc. Note that theflatness of the back surface s2 of the silicon substrate 1 aftergrinding affects the processing accuracy of the through-electrodes.Therefore, dry polishing, etching, or CMP (chemical mechanicalpolishing) is desired to be carried out after the back grind treatment.

Next, as illustrated in FIG. 12, a photoresist film 14 is applied ontothe back surface s2 of the silicon substrate 1 and subjected topatterning by a series of photolithography. Herein, an opening portionis formed in the photoresist film 14 so that part of the siliconsubstrate 1 on which the back-surface-electrode hole portion 7 (seeabove-described FIG. 1) will be processed later is exposed. Morespecifically, the opening-portion formation position of the photoresistfilm 14 is determined at the position of the pad 3 and the bumpelectrode 4 among the components formed in the stage of the presentstep. Examples of the method of adjusting the position include a methodwhich checks the pad 3 by transmission through the silicon of thesubstrate from the back surface s2 of the silicon substrate 1 by using,for example, an infrared microscope and a method which carries outchecking by disposing optical systems on the main surface s1 and theback surface s2 of the silicon substrate 1.

Next, as illustrated in FIG. 13, anisotropic etching is carried out byICP-RIE, thereby forming the back-surface-electrode hole portion 7 inthe back surface s2 of the silicon substrate 1. Note that, for example,SF₆ or C₄F₈ is used as a process gas. Usually, upon dry etching of thesilicon substrate 1, etching is carried out with using a silicon oxidefilm or the like as an etching mask. Therefore, the etching is stoppedat the interlayer insulating film 2 which is formed of a silicon oxidefilm as a primary component. Therefore, the depth of theback-surface-electrode hole portion 7 is determined by the thickness ofthe silicon substrate 1. In this manner, the back-surface-electrode holeportion 7 as explained in above-described FIG. 1 included in thesemiconductor device of the first embodiment can be formed.

Next, as illustrated in FIG. 14, the insulating film 8 is formed on theentire surface of the back surface s2 of the silicon substrate 1including the inner surface of the back-surface-electrode hole portion7, for example, by a CVD method. An insulating film mainly formed of,for example, silicon oxide, silicon nitride, or a polyimide resin isformed as the insulating film 8. Herein, a process gas does not readilyenter the inside of the back-surface-electrode hole portion 7, and theinsulating film 8 deposited on the inside of the back-surface-electrodehole portion 7 becomes thinner than the insulating film 8 depositedoutside of the back-surface-electrode hole portion 7. Note that, uponthe film formation, in the CVD method, film formation is generallycarried out at a temperature of about 300° C. to 500° C. Regarding this,in the manufacturing method of the first embodiment, the insulating film8 may be formed at a lower temperature so that the adhesion layer 12used for pasting the support wafer 13 is not deteriorated and peeledoff.

Next, as illustrated in FIG. 15, in the insulating films formed on theinside of the back-surface-electrode hole portion 7, the insulating film8 that is on the bottom portion in the hole is removed. Herein, theinsulating film 8 is removed until the protruding portion d1 of the bumpelectrode 4 is exposed. However, the removal is adjusted so that thesilicon substrate 1 is not exposed by the etching of the present step,in order to prevent a connection between the back-surface electrode 6(see above-described FIG. 1), which will be formed later, and thesilicon substrate 1. A dry etching that exhibits anisotropy in thedirection perpendicular to the back surface s2 of the silicon substrate1 is carried out. At this point, as described above, the insulating film8 on the inside of the back-surface-electrode hole portion 7 is thincompared with the insulating film 8 that is outside of the hole portion7. Therefore, when the anisotropic etching is carried out in theabove-described manner, the insulating film 8 that is covering thesidewalls and also the thick insulating film 8 that is outside of thehole are remained without being completely removed even when theinsulating film 8 that is on the bottom portion of theback-surface-electrode hole portion 7 is removed to a degree at whichthe protruding portion d1 of the bump electrode 4 is exposed. Thus, inthe periphery of the back-surface-electrode hole portion 7, theinsulating film 8 can be processed so that the protruding portion d1 ofthe bump electrode 4 is exposed and the silicon substrate 1 is in thestate covered with the insulating film 8.

Next, as illustrated in FIG. 16, the back-surface-electrode seed layer 9is formed on the back surface s2 of the silicon substrate 1 includingthe inner surface of the back-surface-electrode hole portion 7, forexample, by a sputtering method. As the formed back-surface-electrodeseed layer 9, for example, stacked films of a Ti film of about 0.02 to0.3 μm and an Au film of about 0.3 to 2 μm are formed. The Ti film isformed in order to improve the adhesiveness between the insulating film8 and the Au film, and the Au film is formed as a seed layer for formingthe back-surface electrode later by a plating method. Other than this,for example, stacked films of a chromium (Cr) film and an Au film may beformed as the back-surface-electrode seed layer 9.

Next, as illustrated in FIG. 17, a photoresist film 15 is formed on theback surface s2-side of the silicon substrate 1 and subjected topatterning by a photolithography method. In this process, an opening isformed in the photoresist film 15 so as to expose theback-surface-electrode seed layer 9 at the location at which theback-surface electrode 6 described with reference to above-describedFIG. 1 is to be formed.

Subsequently, a metal film is formed by carrying out an electrolyticplating method with using the back-surface-electrode seed layer 9 at thepart exposed from the photoresist film 15. As a result, the metal filmis deposited so as to cover the back-surface-electrode seed layer 9, andthe back-surface electrode 6 can be formed. The metal film has a filmthickness that does not completely fill the back-surface-electrode holeportion 7. The metal film has, for example, a single-layer structure ofAu, Cu, Al, Ni, or the like or a multi-layer structure of any of thesemetals. However, as is described later in detail, since the back-surfaceelectrode 6 connects chips by utilizing its plastic deformation, theuppermost surface of the back-surface electrode 6 is desired to be Auwhich readily undergoes plastic deformation. Then, the photoresist film15 is removed, for example, by an organic solvent or oxygen ashing.

Next, as illustrated in FIG. 18, a photoresist film 16 which covers theback-surface-electrode hole portion 7 and the back-surface electrode 6is formed by a photolithography step. Then, the back-surface-electrodeseed layer 9 is subjected to etching with using the photoresist film 16as an etching mask. As a result, part of the back-surface-electrode seedlayer 9 not covered with the photoresist film 16 and the back-surfaceelectrode 6 is removed. For example, a mixed solution of iodide andammonium iodide is used as the etching solution of the Au film, andfluorine is used as the etching solution of the Ti film.

Then, the photoresist film 16 is removed, for example, by an organicsolvent or oxygen ashing. Furthermore, the adhesion layer 12 is removedfrom the silicon substrate 1, thereby peeling off the support wafer 13.For example, if the adhesion layer 12 is thermoplastic, the supportwafer 13 is peeled off by heating. Alternatively, if the support wafer13 is adhered by using, for example, a photoresist film, the supportwafer 13 is peeled off by an organic solvent or the like. Thethrough-electrode included in the semiconductor device of the firstembodiment and having the structure as illustrated in FIG. 19 can beformed by the above-described steps.

In a subsequent step, the wafer-like silicon substrate 1 is singulatedinto chips by blade dicing. Herein, when the chips are singulated afterthe support wafer 13 is peeled off in the above-described manner,although handling becomes difficult, the support wafer 13 can be reused.

When the semiconductor device having the through-electrode having thestructure according to the first embodiment described above is employed,the following effects can be exerted.

In the through-electrode structure according to the first embodiment,the bump electrode 4 has the protruding portion d1, and the protrudingportion has the shape that is inserted in the silicon substrate 1-sidewhen viewed from the pad 3. This has the effect that facilitatesprocessing of the back-surface-electrode hole portion 7, which is formedfrom the surface (back surface s2) of the silicon substrate 1 on theopposite side. This is for the reason that, while the hole portionusually has to be dug down to the back surface of the pad, the necessarydug-down amount can be reduced by the amount corresponding to theprotrusion of the protruding portion d1 of the bump electrode 4 in thefirst embodiment.

Particularly, when the back-surface-electrode hole portion 7 is desiredto reach the pad 3, the interlayer insulating film 2, which is at thebottom of the hole and is not readily processed, has to be processed,and etching has to be stopped without damaging the thin pad 3. Comparedwith this, in the manufacturing method of the first embodiment, theprotruding portion d1 of the bump electrode 4 is formed so as topenetrate through the pad 3; therefore, the processing amount of theinterlayer insulating film 2 can be correspondingly reduced.Furthermore, since the pad 3 is not required to be processed from theback surface s2-side, damage caused on the pad 3 can be reduced. As aresult, the performance can be enhanced in the semiconductor device, inwhich a plurality of semiconductor chips are stacked, withoutdeteriorating the productivity.

Moreover, in the manufacturing method of the first embodiment, asdescribed above, the electrolytic plating method can be employed as themethod of forming the bump electrode 4. The bump electrodes 4 formed bythe electrolytic plating method can be disposed at a smaller distance(pitch), for example, compared with stud bumps. In this manner, when thethrough-electrode having the structure according to the first embodimentis applied, a semiconductor device having a structure suitable forincreasing the number of pins can be realized. As a result, theperformance can be further enhanced in the semiconductor device, inwhich a plurality of semiconductor chips are stacked, withoutdeteriorating productivity.

Second Embodiment

In a second embodiment, a structure which exerts different effects bychanging the shape of the through-electrode in the semiconductor deviceof the above-described first embodiment will be described. Asemiconductor device of the second embodiment has a similarconfiguration and similar effects as the semiconductor device of theabove-described first embodiment except for the configuration describedbelow.

A first structure will be described with reference to FIG. 20. Thethrough-electrode of the semiconductor device of the second embodimenthas a structure similar to that of the through-electrode of thesemiconductor device of the above-described first embodiment.Specifically, the bump electrode 4 formed in the main surface s1-side ofthe silicon substrate 1 has the protruding portion d1, and theprotruding portion d1 penetrates through the pad 3, also penetratesthrough the interlayer insulating film 2, and protrudes to the inside ofthe back-surface-electrode hole portion 7. In other words, this can beexpressed to be the structure that satisfies the following conditions.Specifically, when the silicon substrate 1 is viewed in a plan view, aprotruding-portion diameter r1 which is the diameter of the protrudingportion d1 of the bump electrode 4 is smaller than a hole-portiondiameter r2 which is the diameter of the back-surface-electrode holeportion 7. Furthermore, as a length of the protruding portion d1 of thebump electrode 4, a protruding-portion length t1 which is the length ofthe protruding portion d1 viewed from the surface of the interlayerinsulating film 2 is larger than an interlayer-film thickness t2 whichis the thickness of the interlayer insulating film 2.

Herein, as an example, the case in which two chips (a first chip C1 anda second chip C2) having the through-electrode structures as describedabove are electrically connected with each other will be described. Thethrough-electrode structures of the first chip C1 and the second chip C2are the same. In this case, the back-surface-electrode hole portion 7 ofthe first chip C1 is caulked with the bump electrode 4 of the secondchip C2. In the present specification, “caulking” refers to, forexample, fitting the protruding portion in the hole portion so as tobring them to close contact with each other. In this case, the bumpelectrode 4 of the second chip C2 is fit in the back-surface-electrodehole portion 7 of the first chip C1, and the bump electrode 4 is broughtinto close contact with the sidewalls of the back-surface-electrode holeportion 7. As a result, the back-surface electrode 6 of the first chipC1 formed on the sidewalls of the back-surface-electrode hole portion 7is brought into contact with the bump electrode 4 of the second chip C2.In this manner, the first chip C1 and the second chip C2 can beelectrically connected with each other.

Furthermore, a following effect is also provided. In the semiconductordevice of the second embodiment, in the through-electrode structurethereof, the bottom portion of the back-surface electrode 6 is pushed upby the protruding portion d1 of the bump electrode 4. In other words,the back-surface electrode 6 is formed so as to be shallower than thedepth of the back-surface-electrode hole portion 7. Therefore, when thebump electrode 4 of the second chip is fit in the back-surface-electrodehole portion 7 of the first chip C1, the bump electrode 4 is crushed andundergoes plastic deformation in a lateral direction; thus, a strongercaulking connection can be realized. As a result, in the semiconductordevice, in which a plurality of semiconductor chips are stacked, thestability can be improved.

Next, a second structure will be described with reference to FIG. 21. Inthe second structure, the magnitude relation between theprotruding-portion diameter r1 of the bump electrode 4 and thehole-portion diameter r2 of the back-surface-electrode hole portion 7 isthe same as the above-described first structure. More specifically, theprotruding-portion diameter r1 is smaller than the hole-portion diameterr2. Furthermore, in the second structure, the protruding-portion lengtht1 of the bump electrode 4 is smaller than the interlayer-film thicknesst2. Therefore, in the second structure, the protruding portion d1 of thebump electrode 4 is formed so as to protrude within the interlayerinsulating film 2 without reaching the silicon substrate 1.

A method of manufacturing the semiconductor device having thethrough-electrode of the second structure will be described. First, inthe same manner with the above-described method of FIG. 4, the pluralityof semiconductor elements, the interlayer insulating film 2, and thepads 3 are formed on the main surface s1 of the silicon substrate 1.

Then, as illustrated in FIG. 22, the bump-electrode hole portion 10 isformed in the same manner as the above-described method of FIG. 5.However, in the present step, the bump-electrode hole portion 10 isformed so as not to reach the silicon substrate 1. In other words, thebump-electrode hole portion 10 is formed by carrying out anisotropicetching so that the etching stops in the middle of the interlayerinsulating film 2. In the subsequent process, steps similar to those ofabove-described FIGS. 6 to 12 are carried out.

Subsequently, as illustrated in FIG. 23, in the same manner as theabove-described method of FIG. 13, the back-surface-electrode holeportion 7 is formed from the back surface s2 of the silicon substrate 1.However, in the present step, the back-surface-electrode hole portion 10is formed so as to penetrate through the silicon substrate 1 and togrind part of the interlayer insulating film 2. In this case, theprocess gas such as SF₆ or C₄F₈ used for etching the silicon substrate 1is changed to C₃F₈, Ar, CHF₄, or the like for etching the interlayerinsulating film 2. In this process, without forming a new etching mask,the interlayer insulating film 2 is subjected to anisotropic etchingwith using the residue of the photoresist film 14 and the back surfaces2 of the silicon substrate 1 as an etching mask. Particularly, theanisotropic etching is carried out until the protruding portion d1(bump-electrode seed layer 5) of the bump electrode 4 in the interlayerinsulating film 2 is exposed.

Then, steps similar to those of above-described FIGS. 14 to 19 arecarried out, thereby forming the through-electrode having the secondstructure of the second embodiment illustrated in above-described FIG.21.

Even in the method of forming the back-surface-electrode hole portion 7as described above, etching to penetrate through the interlayerinsulating film 2 and reach the pad 3 is not necessary to be carriedout. This is for the reason that, similarly to the above-described firstembodiment, the bump electrode 4 has the protruding portion d1 whichpenetrates through the pad 3, and the etching is required to be carriedout to expose at least the protruding portion d1. By virtue of themethod that forms the hole portion from both sides of the siliconsubstrate 1 in this manner, the following effects can be obtained assame as the above-described first embodiment. Specifically, since theprotruding portion d1 of the bump electrode 4 is formed so as topenetrate through the pad 3, the processing amount of the interlayerinsulating film 2 can be correspondingly reduced. Furthermore, since thepad 3 is not required to be processed from the back surface s2-side,damage caused on the pad 3 can be reduced. As a result, in thesemiconductor device in which a plurality of semiconductor chips arestacked, the performance can be enhanced without deteriorating theproductivity.

Furthermore, according to the second structure, the structure in whichthe protruding portion d1 of the bump electrode 4 does not protrude tothe inside of the back-surface-electrode hole portion 7 can be obtained.As a result, the back-surface electrode 6 (and theback-surface-electrode seed layer 9 in the below layer thereof) can beformed to be flatter. As a result, in the semiconductor device in whicha plurality of semiconductor chips are stacked, the performance can befurther enhanced without deteriorating the productivity.

On the other hand, in the first structure in which the protrudingportion d1 of the bump electrode 4 reaches the inside of the siliconsubstrate 1, the structure having the shallower back-surface electrode6, compared with the second structure, can be obtained. This structurecan further strengthen the caulking connection as described above.

Moreover, the through-electrodes having the first and second structureshave the structure in which misalignment does not readily occur when aplurality of chips are stacked. This is for the reason that, in thesecond structure, the back-surface-electrode hole portion 7 into whichthe bump electrode 4 is to be fit has a wide width and that the rangethat can allow planar misalignment of the bump electrode 4 is wide.Since the misalignment upon connection between chips is small in thismanner, the structure can be said to be suitable for miniaturization andincreasing the number of pins of a semiconductor device. As a result, inthe semiconductor device in which a plurality of semiconductor chips arestacked, the performance can be further enhanced without deterioratingthe productivity.

Next, a third structure will be described with reference to FIG. 24. Inthe third structure, the relation between the protruding-portion lengtht1 of the bump electrode 4 and the interlayer-film thickness t2 is thesame as the above-described second structure. More specifically, theprotruding-portion length t1 is smaller than the interlayer-filmthickness t2. Therefore, similar to the above-described secondstructure, the third structure also has the effect that the inner wallof the back-surface-electrode hole portion 7 so as to be furtherflatter, thereby being more readily covered with the back-surfaceelectrode 6. Furthermore, in the third structure, the protruding-portiondiameter r1 of the bump electrode 4 is larger than the hole-portiondiameter r2 of the back-surface-electrode hole portion 7. In otherwords, in the third structure, when viewed in a plan view, theback-surface-electrode hole portion 7 is formed to be within theprotruding portion d1 of the bump electrode 4.

The through-electrode of the third structure can be formed as same asthe through-electrode having the above-described second structure,except that the magnitude relation of the diameters of thebump-electrode hole portion 10 and the back-surface-electrode holeportion 7 is set to be the relation described above.

The through-electrode such as the third structure is the structure thatdoes not readily cause misalignment upon formation of the electrode holeportions 7 and 10. This is for the reason that the bump-electrode holeportion 10, which is formed first, has a wide width, and that theback-surface-electrode hole portion 7 is required to be formed to beoverlapped with any position of the bump-electrode hole portion 10 in aplan view. In this manner, employing the third structure to thethrough-electrode of the semiconductor device of the second embodimenthas an advantage in terms of manufacturing method. As a result, in thesemiconductor device in which a plurality of semiconductor chips arestacked, the performance can be further enhanced without deterioratingthe productivity.

On the other hand, in the first and second structures in which theprotruding-portion diameter r1 of the bump electrode 4 is smaller thanthe hole-portion diameter r2 of the back-surface-electrode hole portion7, misalignment upon stacking of a plurality of chips does not readilyoccur as described above. Since the misalignment upon connection betweenchips is small in this manner, the structures can be said to be suitablefor miniaturization and increasing the number of pins of a semiconductordevice. As a result, in the semiconductor device in which a plurality ofsemiconductor chips are stacked, the performance can be further enhancedwithout deteriorating the productivity.

Next, a fourth structure will be described with reference to FIG. 25. Inthe fourth structure, the relation between the protruding-portiondiameter r1 of the bump electrode 4 and the hole-portion diameter r2 ofthe back-surface-electrode hole portion 7 is the same as theabove-described third structure, and the protruding-portion diameter r1is larger than the hole-portion diameter r2. In other words, when viewedin a plan view, the back-surface-electrode hole portion 7 is formed tobe within the protruding portion d1 of the bump electrode 4. Therefore,as well as the above-described third structure, the fourth structurealso has the effect that misalignment upon formation of the electrodehole portions 7 and 10 does not readily occur. As a result, in thesemiconductor device in which a plurality of semiconductor chips arestacked, the performance can be further enhanced without deterioratingthe productivity.

Furthermore, in the fourth structure, the relation between theprotruding-portion length t1 of the bump electrode 4 and theinterlayer-film thickness t2 is the same as the above-described firststructure, and the protruding-portion length t1 is larger than theinterlayer-film thickness t2. More specifically, when viewed in a crosssection, the protruding portion d1 of the bump electrode 4 penetratesthrough the interlayer insulating film 2 and reaches the inside of thesilicon substrate 1. Therefore, similar to the above-described firststructure, the fourth structure also has the effect that enablesstronger caulking connection when chips are stacked and connected. As aresult, in the semiconductor device in which a plurality ofsemiconductor chips are stacked, the performance can be further enhancedwithout deteriorating the productivity.

Herein, the above-described fourth structure is the structure that canbe in contact with the silicon substrate 1 since the protruding portiond1 of the bump electrode 4 is not within the back-surface-electrode holeportion 7. The contact between the protruding portion d1 and the siliconsubstrate 1 having conductivity is a cause of generation of a leakagecurrent. Therefore, a protective insulating film 17 has to be formed atleast on the boundary part of the protruding portion d1 of the bumpelectrode 4 and the silicon substrate 1 so that they are notelectrically connected with each other. FIG. 25 illustrates, as anexample, a structure in which the protective insulating film 17 isdisposed so as to integrally cover the part from the inner walls of thebump-electrode hole portion 10 to the surface of the interlayerinsulating film 2, which is outside of the hole portion 10.

Meanwhile, the bump electrode 4 (the bump-electrode seed layer 5 in thebelow layer thereof) and the pad 3 have to be electrically connectedwith each other. Therefore, at a main part p1 on the pad 3, a hole isprovided in the protective insulating film 17 covering the pad 3 and thepad 3 and bump electrode 4 are brought into contact with each other.Meanwhile, the bump electrode 4 (the bump-electrode seed layer 5 in thebelow layer thereof) and the back-surface electrode 6 (theback-surface-electrode seed layer 9 in the below layer thereof) have tobe electrically connected with each other. Therefore, in this structure,at a main part p2 at the boundary part of them, a hole is provided inthe protective insulating film 17, so that the bump electrode 4 and theback-surface electrode 6 are brought into contact with each other.

Hereinafter, a method of manufacturing the semiconductor device havingthe through-electrode having such fourth structure will be described.First, in the same manner as the above-described method of FIG. 4, theplurality of semiconductor elements, the interlayer insulating film 2,and the pads 3 are formed on the main surface s1 of the siliconsubstrate 1. Then, as illustrated in FIG. 26, the bump-electrode holeportion 10 is formed in the same manner as the above-described method ofFIG. 5.

Next, as illustrated in FIG. 27, the protective insulating film 17 isformed on the entire surface of the interlayer insulating film 2including the bump-electrode hole portion 10 on the main surface s1-sideof the silicon substrate 1. For example, a silicon oxide film is formedas the protective insulating film 17, for example, by a CVD method orsputtering method.

Next, as illustrated in FIG. 28, a contact hole is formed to expose thepad 3 at the main part p1 which is a part of the protective insulatingfilm 10 covering the pad 3. For example, a photolithography method oretching method is used in this process.

Next, as illustrated in FIG. 29, the bump-electrode seed layer 5 isformed so as to cover the protective insulating film 10. Thebump-electrode seed layer 5 is formed in the same manner as theabove-described method of FIG. 6. At this point, the state in which thepad 3 and the bump-electrode seed layer 5 are in contact with each othervia the contact hole of the protective insulating film 10 at the mainpart p1 formed in the above-described step of FIG. 28 is achieved.

Next, as illustrated in FIG. 30, in the same manner as theabove-described method of FIG. 7, the photoresist film 11 is formed, anda hole having a desired shape is formed by a photolithography method.The shape of the hole is formed similarly to that in above-describedFIG. 7.

Next, as illustrated in FIG. 31, the bump electrode 4 is formed by anelectrolytic plating method in the same manner as the above-describedmethod of FIG. 8. The bump electrode 4 is formed also in thebump-electrode hole portion 10, and this part serves as the protrudingportion d1 of the bump electrode 4.

Next, as illustrated in FIG. 32, in the same manner as theabove-described method of FIG. 9, the exposed part of the bump-electrodeseed layer 5 is removed by maskless etching. Through the above-describedsteps, the structure in which the protective insulating film 17 isdisposed on the boundary part at which the bump electrode 4 (thebump-electrode seed layer 5) and the silicon substrate 1 can be incontact with each other can be formed.

Next, as illustrated in FIG. 33, in the same manner as theabove-described method of FIG. 10, the adhesion layer 12 and the supportwafer 13 are formed. Then, in the same manner as the above-describedmethod of FIG. 11, the silicon substrate 1 is subjected to a back grindtreatment, thereby reducing the thickness thereof; and, subsequently,the back surface s2 of the silicon substrate 1 is planarized, forexample, by CMP.

Next, as illustrated in FIG. 34, in the same manner as theabove-described method of FIGS. 12 and 13, the back-surface-electrodehole portion 7 is formed from the back surface s2 of the siliconsubstrate 1 to the bottom portion of the bump-electrode hole portion 10.

Next, as illustrated in FIG. 35, in the same manner as theabove-described method of FIG. 14, the insulating film 8 is formed fromthe back surface s2-side of the silicon substrate 1 including theback-surface-electrode hole portion 7.

Next, as illustrated in FIG. 36, a photoresist film 18 is formed on theback surface s2-side of the silicon substrate 1. In this process, thephotoresist film 18 is spin-coated by using, for example, a spinner. Inthis process, the photoresist film 18 is formed to be prevented fromentering the inside of the back-surface-electrode hole portion 7 byselecting the type and application conditions of the photoresist film18.

Next, as illustrated in FIG. 37, the photoresist film 18 applied in theprevious step is subjected to exposure and development, therebyproviding a hole portion 19 in the photoresist film 18. In this process,when viewed in a plan view, the hole portion 19 is formed at a positioninside the back-surface-electrode hole portion 7. Then, as illustratedin FIG. 38, while using the photoresist film 18 as an etching mask, theinsulating film 8 and the protective insulating film 17 in the belowlayer thereof are subjected to anisotropic etching to be removed. As aresult, the bump-electrode seed layer 5, which constitutes the bumpelectrode 4, is exposed at the main part p2 at the bottom of theback-surface-electrode hole portion 7. Then, the photoresist film 18 isremoved by an organic solvent such as acetone or oxygen ashing.

In the present step, as described with reference to above-described FIG.36, the photoresist film 18 is applied not to enter the inside of theback-surface-electrode hole portion 7. As a result, when the photoresistfilm 18 is removed in the above-described step of FIG. 38, the step inwhich the resist film does not readily remain in the inside of the holecan be carried out without the need of actively cleaning the inside ofthe back-surface-electrode hole portion 7. The state in which the resistfilm remains in the hole can be a cause of defective etching in a laterstep or a cause of peel-off of the electrode. Therefore, by virtue ofthe present step, the semiconductor device having a higher reliabilitycan be formed.

In a subsequent step, as illustrated in FIG. 39, in the same manner asthe above-described method of FIG. 10, the back-surface-electrode seedlayer 9 is formed from the back surface s2-side of the silicon substrate1 including the inner surface of the back-surface-electrode hole portion7. In this step, the bump-electrode seed layer 5 and theback-surface-electrode seed layer 9 are brought into contact with eachother at the main part p2 at which the insulating film 8 and theprotective insulating film 17 are removed in the previous step and thebump-electrode seed layer 5 is exposed.

Next, as illustrated in FIG. 40, in the same manner as the method ofabove-described FIG. 17, the back-surface electrode 6 is formed. In thisprocess, at the main part p2 in the back-surface-electrode hole portion7, the back-surface electrode 6 and the bump electrode 4 areelectrically connected with each other via the back-surface-electrodeseed layer 9 and the bump-electrode seed layer 10, and thus thethrough-electrode structure can be formed.

Next, as illustrated in FIG. 41, in the same manner as the method ofabove-described FIGS. 18 and 19, the back-surface-electrode seed layer 9is processed. The semiconductor device having the through-electrodehaving the fourth structure of the second embodiment can be formed bythe above steps.

Meanwhile, the structure in which the protective insulating film 17 isprovided to the lower part of the bump electrode 4 and thebump-electrode seed layer 5 like the through-electrode of theabove-described fourth structure may be employed for anotherconfiguration. Examples will be given below.

As illustrated in FIG. 42, the protective insulating film 17 asdescribed above may be provided to the structure in which theprotruding-portion diameter r1 of the bump electrode 4 is smaller thanthe hole-portion diameter r2 of the back-surface electrode 6, and theprotruding-portion length t1 of the bump electrode 4 is larger than theinterlayer-film thickness t2 of the interlayer insulating film 2. Alsoin this through-electrode structure, the caulking connection force isimproved as the bottom level of the back-surface-electrode hole portion7 is raised.

Also, as illustrated in FIG. 43, the protective insulating film 17 asdescribed above may be provided to the structure in which theprotruding-portion diameter r1 of the bump electrode 4 is smaller thanthe hole-portion diameter r2 of the back-surface electrode 6, and theprotruding-portion length t1 of the bump electrode 4 is smaller than theinterlayer-film thickness t2 of the interlayer insulating film 2.

Also, as illustrated in FIG. 44, the protective insulating film 17 asdescribed above may be provided to the structure in which theprotruding-portion diameter r1 of the bump electrode 4 is larger thanthe hole-portion diameter r2 of the back-surface electrode 6, and theprotruding-portion length t1 of the bump electrode 4 is smaller than theinterlayer-film thickness t2 of the interlayer insulating film 2.

On the other hand, compared with the fourth structure and themodification examples thereof, the protective insulating film 17 asdescribed above is not required to be formed in the above-describedfirst, second, and third structures since the protruding portion d1 ofthe bump electrode 4 and the silicon substrate are not in contact inthese structures. From this point of view, as to the first, second, andthird structures, the number of manufacturing steps for formation andprocessing of the protective insulating film 17 as described above canbe reduced. As a result, in the semiconductor device in which aplurality of semiconductor chips are stacked, the performance can befurther enhanced without deteriorating the productivity.

Third Embodiment

A semiconductor device of a third embodiment will be described withreference to FIG. 45. The semiconductor device of the third embodimenthas a configuration in which a plurality of semiconductor chips havingthrough-electrodes like those of the above-described first and secondembodiments are stacked. Herein, the semiconductor chips are stacked inthe manner as described with reference to above-described FIG. 20.

FIG. 45 illustrates the semiconductor device including the stackedplurality of chips (first chip C1, second chip C2, and third chip C3)having the through-electrodes of the third embodiment. The chips aremutually connected by physical caulking by injecting andpressure-welding the bump electrode 4 formed on an upper-level chip (forexample, the second chip C2) into and with the hollowback-surface-electrode hole portions 7 formed in a lower-level chip (forexample, the first chip C1). The bump electrodes 4 of the chip of thelowermost layer (in this case, the first chip C1) are joined withelectrodes 21 of a wiring board 20, thereby achieving the state in whichthe chip is electrically connected with the wiring board 20. Moreover,solder bumps 22 are formed on the lower side of the wiring board 20 andare used for connection with outside. The solder bumps 22 areelectrically connected with the electrodes 21 of the wiring board 20 viainternal wiring (not illustrated), etc. of the wiring board 20. In otherwords, the chips C1, C2, and C3 are electrically connected mutually viathe through-electrodes and are further electrically connected with thesolder bumps 22 via the electrodes 21 of the wiring board 20.

After the chips are stacked on the wiring board 20, the gaps of theplurality of chips (first chip C1, second chip C2, and third chip C3)and the wiring board 20 is filled with an underfill resin 23. As aresult, the mechanical strength is enlarged so as to enhance thehandling ability, and the device is protected from the externalenvironment.

In the semiconductor device having the above-described configuration,different effects can be exerted depending on the outer shape of thebump electrode 4 or the outer shape of the back-surface-electrode holeportion 7. Hereinafter, the effects brought about to the semiconductordevice by the difference in the outer shapes will be described indetail. First, the outer shape of the corresponding bump electrode 4 andthe outer shape of the back-surface-electrode hole portion 7 will bedescribed with reference to FIG. 46. Since the back-surface-electrodehole portion 7 is covered with the back-surface electrode 6 in practice,hereinafter, when the outer shape of the back-surface-electrode holeportion 7 is referred to, it expresses the outer shape formed by theback-surface electrode 6 covering the outer shape theback-surface-electrode hole portion 7.

FIG. 46A is an explanatory diagram describing the outer shape of thebump electrode 4. A cross-sectional view of the part of the bumpelectrode 4 exposed above the pad 3 is illustrated on the top, and aplan view of the bump electrode 4 is illustrated on the bottom. Asdescribed above, when viewed in the cross section, the sidewall of thebump electrode 4 has the inclination which makes the width increase(diameter of the bump electrode 4 is increased) toward the siliconsubstrate 1. Meanwhile, when viewed in the plan view, the bump electrode4 is circular. FIG. 46B is an explanatory diagram describing the outershape of the back-surface-electrode hole portion 7. A cross-sectionalview of the through-electrode including the back-surface electrode 6 isillustrated on the top, and a plan view of the periphery of theback-surface-electrode hole portion 7 is illustrated on the bottom. Theshape of the perimeter of the opening portion of theback-surface-electrode hole portion 7 is circular when viewed in theplan view. Herein, as to the inclined surface forming the sidewall ofthe bump electrode 4, the diameter of the bottom portion, which is thewidest, is larger than the diameter of the back-surface-electrode holeportion 7.

FIG. 47 is an explanatory diagram explaining the state in which both thechips C1 and C2 are electrically connected to each other by insertingthe bump electrode 4 of the second chip C2 into theback-surface-electrode hole portion 7 of the first chip C1. Across-sectional view of the chips is illustrated on the left side, and aplan view of the periphery of the back-surface-electrode hole portion 7of the first chip C1 is illustrated on the right side. As is understoodfrom FIG. 47, when both the chips C1 and C2 are to be connected witheach other, the inclined surface forming the sidewall of the bumpelectrode 4 of the second chip C2 is brought into contact with thecircumferential part forming the bore of the back-surface-electrode holeportion 7 of the first chip C1 and covers the inside of theback-surface-electrode hole portion 7. In this state, the bump electrode4 is further thrust into the back-surface-electrode hole portion 7 (seeabove-described FIG. 45), thereby achieving a caulking connection.

Particularly, like the above-described example, when the shape of theperimeter of the opening portion of the back-surface-electrode holeportion 7 of the first chip C1 and the planar shape of the bumpelectrode 4 are the same circular shape, the back-surface-electrode holeportion 7 is sealed by the bump electrode 4 in the process of carryingout the caulking connection.

FIGS. 48A, 48B, and 48C illustrate the bump electrodes 4 having shapesother than a precise circle (for example, polygonal shape, oval shape,etc.) as the planar shape thereof. FIG. 48A illustrates an example of atriangular shape, FIG. 48B illustrates an example of a rectangularshape, and FIG. 48C illustrates an example of an oval shape. In each ofthe cases, if the shape of the perimeter of the opening portion of theback-surface-electrode hole portion 7 of the first chip C1 is a precisecircular shape, sealing of the hole like above-described FIG. 47 is notmade. This is for the reason that the opening portion of theback-surface-electrode hole portion 7 of the first chip C1 and thesidewall surface of the bump electrode 4 of the second chip C2 are incontact with each other by points, and gaps are generated between them.This is caused since the shape of the perimeter of the opening portionof the back-surface-electrode hole portion 7 of the first chip C1 andthe planar shape of the bump electrode 4 of the second chip C2 aredifferent from each other. In FIGS. 48A, 48B, and 48C, the triangularshape and the rectangular shape are illustrated as examples of the bumpelectrode 4 having a polygonal shape as the planar shape thereof.However, similar effects can be obtained even when the bump electrode 4has a polygonal shape of a higher order. In that case, the bumpelectrode 4 of the second chip C2 is brought into contact with theperimeter of the opening portion of the back-surface-electrode holeportion 7 of the first chip C1 by more points.

Similar effects can be also obtained when the planar shape of theperimeter of the opening portion of the back-surface-electrode holeportion 7 has a shape other than the precise circle (for example,polygonal shape, oval shape, etc.). Examples of the shapes areillustrated in FIGS. 49A and 49B. FIG. 49A illustrate an example inwhich the shape of the perimeter of the opening portion of theback-surface-electrode hole portion 7 of the first chip C1 is arectangular shape and FIG. 49B illustrates an example of an example ovalshape. In each of the examples, if the planar shape of the bumpelectrode of the second chip C2 is a precise circular shape, the sealingof the inside of the hole as above-described FIG. 47 is not made. Thereason is the same as that explained in above-described FIGS. 48A-49C.In FIGS. 49A and 49B, the rectangular shape is illustrated as an exampleof the planar shape of the back-surface-electrode hole portion 7 havinga polygonal shape as the planar shape. However, similar effects can beexerted even when the shape is a triangular shape or a polygonal shapeof a higher order. In the example of the polygonal shape of a higherorder, the perimeter of the opening portion of theback-surface-electrode hole portion 7 of the first chip C1 is broughtinto contact with the bump electrode 4 of the second chip C2 by morepoints.

For example, when sealing of the inside of the hole as illustrated inabove-described FIG. 47 is made when the plurality of chips having thethrough-electrode structures are subjected to caulking connection, theunderfill resin 23 illustrated in above-described FIG. 45 does not enterthe inside of the back-surface-electrode hole portion 7, and air remainsin the inside of the through-electrode.

On the other hand, sealing in the back-surface-electrode hole portion 7is prevented by applying the back-surface electrode having any of thestructures described with reference to above-described FIGS. 48A, 48B,and 48C and FIGS. 49A and 49B like the semiconductor device of the thirdembodiment. More specifically, gaps are generated between theback-surface electrode 6 of the first chip C1 and the bump electrode 4of the second chip C2. Therefore, when the underfill resin 23 flows in,the air in the back-surface-electrode hole portion 7 is pushed out, andthe underfill resin 23 can be filled therein. Moreover, compared withthe case in which the back-surface electrode 6 and the bump electrode 4are in close contact with each other, the contacting area upon thecaulking connection is reduced when they are in contact with each otherby points like the third embodiment, and the caulking connection can bemade even with a low load. As a result, in the semiconductor device inwhich a plurality of semiconductor chips are stacked, the performancecan be further enhanced without deteriorating the productivity.

The firmness of the caulking connection can be varied also by theinclination angle of the sidewall of the bump electrode 4. In relationto this, description will be given with reference to FIGS. 50A and 50B.As described above, the bump electrode 4 has a tapered shape, in whichthe sidewall thereof is inclined, at the part exposed above the pad 3.

FIG. 50A illustrates a structure in which the sidewall of the bumpelectrode 4 of the second chip C2 has a low-inclination tapered shape.In the semiconductor device of the third embodiment, the sidewall of thebump electrode 4 being the low inclination means that a taper angle v1which is the angle formed by the sidewall of the bump electrode 4 andthe main surface s1 of the silicon substrate 1 is larger than or equalto 45 degrees and smaller than 70 degrees. FIG. 50B illustrates astructure in which the sidewall of the bump electrode 4 of the secondchip C2 has a tapered shape with a steep inclination. In thesemiconductor device of the third embodiment, mentioning that thesidewall of the bump electrode 4 having a steep inclination means that ataper angle v2 which is the angle formed by the sidewall of the bumpelectrode 4 and the main surface s1 of the silicon substrate 1 is largerthan or equal to 70 degrees and smaller than 90 degrees.

When the tapered shape of the sidewall of the bump electrode 4 has a lowinclination, the tip diameter of the bump electrode 4 can be reduced;therefore, misalignment between chips upon chip connection does notreadily occur. Moreover, in this case, the contact area between the bumpelectrode 4 and the back-surface electrode 6 upon the caulkingconnection is small. Therefore, the load for joint required for thecaulking connection can be further reduced.

On the other hand, when the tapered shape of the sidewall of the bumpelectrode 4 has the steep inclination, the contact area between the bumpelectrode 4 and the back-surface electrode 6 upon the caulkingconnection is increased. Therefore, among the plurality of chips stackedby the caulking connection, the joint force can be increased. Note thatthe bump electrode 4 having a columnar shape in which the bumpupper-surface size and the bump lower-surface size are the same hassimilar characteristics as the case in which the tapered shape of thesidewall of the bump electrode 4 has a steep inclination.

To change the taper angles v1 and v2 of the sidewall of the bumpelectrode 4, in the manufacturing method described with reference toabove-described FIG. 7, etc., the outer shape of the pattern is changedby changing the temperature inclination upon heating of the photoresistfilm 11, thereby arbitrarily controlling the taper angles v1 and v2.

In the semiconductor device in which chips having the through-electrodestructures are mutually stacked and subjected to caulking connection,there are requirements to reduce the load required for joint or toincrease the joint force and so forth. In relation to these, asdescribed above, according to the semiconductor device of the thirdembodiment, these factors can be arbitrarily adjusted by changing theshapes of the bump electrode 4 and the back-surface-electrode holeportion 7 in a plan view or by changing the taper angles v1 and v2 ofthe inclined sidewall of the bump electrode 4. More specifically, whenthe load for the joint of the caulking connection is to be reduced,there is a method in which the shape of the bump electrode 4 or theback-surface-electrode hole portion 7 in a plan view is changed to, forexample, a polygonal shape or a method in which the taper angles v1 andv2 of the sidewall of the bump electrode 4 are caused to have a lowinclination. Also, when the joint force of the caulking connection is tobe increased, there is a method in which the planar shapes of the bumpelectrode 4 and the back-surface-electrode hole portion 7 are changed tosimilar precise circular shapes, or a method in which the taper anglesv1 and v2 of the sidewall of the bump electrode 4 is caused to have asteep inclination.

In this manner, according to the semiconductor device according to thethird embodiment, the load required for joint of the semiconductor chipshaving the through-electrodes and the joint force thereof can bearbitrarily adjusted. As a result, in the semiconductor device in whicha plurality of semiconductor chips are stacked, the performance can befurther enhanced without deteriorating the productivity.

In the foregoing, the invention made by the inventors of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention.

For example, in the above-described third embodiment, the structure inwhich the shape of the bump electrode 4 or the back-surface-electrodehole portion 7 is changed and the structure in which the taper angles v1and v2 of the sidewall of the bump electrode 4 are changed areseparately illustrated. These configurations are more effective whenused together.

The present invention is applicable to the semiconductor industrynecessary for carrying out information processing, for example, inpersonal computer, mobile devices, etc.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor substrate having a main surface and a back surfacepositioned on an opposite side to the main surface; a first insulatingfilm formed on the main surface of the semiconductor substrate; a firsthole formed in the first insulating film; a second hole formed in theback surface of the semiconductor substrate; a bump electrode disposedover the first insulating film and having a protruding portion which isformed at least in the first hole and which reaches the inside of thesemiconductor substrate in a cross-sectional view; a second insulatingfilm formed on a side surface of the second hole; and a conductive filmformed in the second hole and electrically connected to the bumpelectrode, wherein, in a planar view, a diameter of the protrudingportion is smaller than a diameter of the second hole; and wherein theconductive film is connected to a side surface and a bottom surface ofthe protruding portion; wherein the first hole is entirely filled withthe bump electrode; and wherein the second hole is not entirely filledwith the conductive film.
 2. The semiconductor device according to claim1, wherein a protective insulating film is formed at a boundary portionbetween the bump electrode and the semiconductor substrate so that thebump electrode and the semiconductor substrate are electricallyinsulated to each other.
 3. The semiconductor device according to claim1, wherein, in a planar view, a shape of a perimeter of the second holeis circular and a shape of the bump electrode is polygonal.
 4. Thesemiconductor device according to claim 1, wherein, in a planar view, ashape of a perimeter of the second hole is polygonal and a shape of thebump electrode is circular.
 5. The semiconductor device according toclaim 1, wherein the bump electrode has a shape in which a sidewall hasan inclination at a portion exposed above the second insulating film. 6.The semiconductor device according to claim 5, wherein the bumpelectrode has an inclination at an angle greater than or equal to 45degrees to less than 70 degrees at a portion exposed above the secondinsulating film.
 7. The semiconductor device according to claim 5,wherein the bump electrode has an inclination at an angle greater thanor equal to 70 degrees to less than 90 degrees at a portion exposedabove the second insulating film.
 8. The semiconductor device accordingto claim 1, wherein a pad is formed between the first insulating filmand the bump electrode, and wherein the second hole does not reach thepad.
 9. The semiconductor device according to claim 1, wherein the bumpelectrode includes a first seed layer and a first metal film, whereinthe first seed layer includes Ti or TiW, and wherein the first metalfilm includes Au, Cu, Al or Ni.
 10. The semiconductor device accordingto claim 9, wherein the conductive film includes a second seed layer anda second metal film, wherein the second seed layer includes Ti and Au,or Cr and Au, and wherein the second metal film includes Au, Cu, Al orNi.
 11. A semiconductor device comprising: a semiconductor substratehaving a main surface and a back surface positioned on an opposite sideto the main surface; a first insulating film formed on the main surfaceof the semiconductor substrate; a first hole formed in the firstinsulating film; a second hole formed in the back surface of thesemiconductor substrate; a bump electrode disposed over the firstinsulating film and having a protruding portion which is formed at leastin the first hole and which reaches the inside of the semiconductorsubstrate in a cross-sectional view; a second insulating film formed ona side surface of the second hole; and a conductive film formed in thesecond hole and electrically connected to the bump electrode, wherein,in a planar view, a diameter of the protruding portion is smaller than adiameter of the second hole; wherein the conductive film is connected toa side surface and a bottom surface of the protruding portion; wherein apad is formed between the first insulating film and the bump electrode;and wherein the second hole does not reach the pad.
 12. Thesemiconductor device according to claim 11, wherein a protectiveinsulating film is formed at a boundary portion between the bumpelectrode and the semiconductor substrate so that the bump electrode andthe semiconductor substrate are electrically insulated to each other.13. The semiconductor device according to claim 11, wherein, in a planarview, a shape of a perimeter of the second hole is circular and a shapeof the bump electrode is polygonal.
 14. The semiconductor deviceaccording to claim 11, wherein, in a planar view, a shape of a perimeterof the second hole is polygonal and a shape of the bump electrode iscircular.
 15. The semiconductor device according to claim 11, whereinthe bump electrode has a shape in which a sidewall has an inclination ata portion exposed above the second insulating film.
 16. Thesemiconductor device according to claim 15, wherein the bump electrodehas an inclination at an angle greater than or equal to 45 degrees toless than 70 degrees at a portion exposed above the second insulatingfilm.
 17. The semiconductor device according to claim 15, wherein thebump electrode has an inclination at an angle greater than or equal to70 degrees to less than 90 degrees at a portion exposed above the secondinsulating film.
 18. The semiconductor device according to claim 11,wherein the bump electrode includes a first seed layer and a first metalfilm, wherein the first seed layer includes Ti or TiW, and wherein thefirst metal film includes Au, Cu, Al or Ni.
 19. The semiconductor deviceaccording to claim 18, wherein the conductive film includes a secondseed layer and a second metal film, wherein the second seed layerincludes Ti and Au, or Cr and Au, and wherein the second metal filmincludes Au, Cu, Al or Ni.